How to drop weight for weigh in?

My cousin recently reduced considerable weight for a weigh in. To reduce extra pounds he went for a major change in his daily diet. He avoided sodium and all fast foods and fried foods. He took only raw vegetables, fruits and lots of water. He worked out vigorously under the guidance of his trainer and reached his aim. There are also methods like low protein diet and low carbohydrate diet wherein the fat content of the body is depleted along with some muscle mass. Taking only food supplements and dehydrating techniques like use of laxatives and diuretics are some other methods for immediate weight loss.